I am having some stumbling at high rpms. The car starts jerking pretty hard once it passes 3,4k.It idles well . I have rebuilt the engine it pretty much stock except for longtube headers x-pipe and a bbk cold air intake. I have replaced maf, put in a better fuel pump, fuel tank , ignition coil, wires spark plugs, 02 sensors and some other minor parts. I have recently purchased a remanufactured ecm due to the old one having some water damage, the car ran a lot better but it still stumbles not as bad but still does. I am thinking i need to tune it because I ran out of options. And how can I tune it.? I also don't have an egr i have a plug for the connector and a plate on the intake and I don't have a smog system i plugged the back of the heads during the rebuild. I live in a state that doesn't check emissions once the car is 25+ yrs
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